1. Field of the Invention
The invention relates to location services, and in particular, but not exclusively, to processing of location information in a plurality of location information entities associated with a communication system.
2. Description of the Related Art
Communication systems providing mobility for the users thereof are known. A well-known example of such mobile communication systems is the public land line mobile network (PLMN), of which cellular communications networks are an example. Another example is a mobile communication system that is based, at least partially, on the use of communication satellites.
In such systems, the mobile network apparatus and/or user equipment such as a mobile station can be employed for provision of information regarding the geographical location of the user equipment and thus the user thereof. An arrangement configured to provide location information is often called by the name location service (LCS) or location information service.
The position of mobile user equipment, and the equipment's user, can be positioned by various techniques. For example, fairly accurate geographical location information can be obtained based on the known satellite based GPS (Global Positioning System). More accurate location information can be obtained through differential GPS techniques. Another proposed satellite based location system is known by the name Galileo.
Another possibility is to use a location service based on a cellular telecommunications system. In this approach, the cells or similar geographically limited radio access entities and associated controllers of the communication system are utilized in the production of at least a rough estimate of the current location of the mobile user equipment. To improve the accuracy of the location information the communication system may be provided with specific location measurement units that provide more accurate information concerning the location of the user equipment within the service area of the cellular system. It is also possible to ascertain a geographical location when the mobile user equipment is located within the coverage area of a visited or “foreign” network. The visited network may be configured to transmit the location of the mobile user equipment back to the home network, e.g. to support services that are based on location information or for the purposes of routing and charging. The particular way in which location information is produced does not form an essential element of the present invention, and is thus not described in any greater detail herein. Location information may also be produced based on information from both the satellite based and the communication system based location systems.
The location service entities provided by the communication system may serve different location service (LCS) clients via appropriate interfaces. The location information may be used for various purposes, such as for location of a mobile telephone that has made an emergency call, for locating vehicles or mobile subscribers and so on. In general, a client such as a user equipment (UE), a service application provided e.g. by means of the Internet or another information communication facility or any other entity wishing to receive location information regarding a user equipment may send a request for such information to the location service provision entity. The location service provisioning entity will then process the request, obtain the required information and generate an appropriate response.
The location information may be processed in one or more specific location service entities implemented either within the cellular system or connected thereto. In a typical operation the location information is provided for the client entity as a result of co-operation of a plurality of location information entities such as servers associated with the location services. The current location specifications allow roaming between location information entities, such as location servers. In practice this means that location information of a target user can be processed in different servers depending on the location of the mobile target user. Therefore the location servers may have different roles depending on the location of the target user and also the origin of the request. The conventional location servers may act in three different roles, namely as a receiving location server, a home location server and a visited location server.
The receiving location server (RLS) is the location server that originally receives a location request from a LCS Client. This request may be communicated over any appropriate interface, for example over a conventional Mobile Location Protocol (MLP) 3.0 interface. At some point the receiving location information service entity may realize that it cannot fulfill the client's request. Therefore the receiving location server may need to initiate “roaming” to other location service entities.
A home location server is the server responsible for enforcing the privacy options setup by the user. A home location server can thus be understood as being a location server that possesses or at least has access to subscriber related information such as the subscriber privacy profile. The home location server may also be capable of performing the actual positioning if the target user (the subscriber) is actually located in the home area. Otherwise, the home location server is responsible for forwarding the request to a visited location server where the positioning will then take place.
The visited location server is the location server responsible for positioning in the area where the target user is currently located. In this role the only responsibility of the location server is to perform the actual positioning of the subscriber.
A given location server may serve in any of the above roles for any given request. Also, a given location server may be responsible for all possible roles for certain requests or it may be responsible for a combination of at least two roles.
Conventionally a location server receiving a location request from another location service entity is expected to interpret its role from the parameters of the request from the requesting location service entity. This means that the decision regarding the role that the location server shall play during the roaming scenarios is left in its entirety to the location server that received the request. However, the parameters received by the location server may not clearly dictate what role the receiving location server is expected to play from the point of view of the requesting location server. Thus it may occur in certain scenarios that the location server concludes that it shall play a role which was not expected by the requesting location server. The confusion is due to the extrapolation of the role of the location server from the parameters received from the requesting location server.
In the event that a location server receiving a request assumes a role not expected by the requesting location server, security holes are possible in the roaming scenarios in accordance with the roaming specifications. A lowered security may be caused, for example, by bypassing of mobile subscriber privacy settings when performing location roaming on the interface between location servers. The problem may result from a combination of various seemingly unrelated factors. For example, the used interface protocol may force the home location server (HLS) and visited location server (VLS) to “assume” their role based on data they receive and the absence or presence of profile data. At the same time the subscriber databases and/or routing tables may not be 100% accurate at all times.
If a location server determines it is not the home location server (HLS) because it cannot find the subscriber profile, it will route the request to another location server. A problem here may be that the home location server may not have the subscriber profile and therefore it may think that it should act as a visited location server (VLS). That is, a server incorrectly acting as a visited location server may i.e. position the subscriber without ever performing any privacy checks and return this data to the requesting entity. It is thus possible that a home location server returns the location result as it would be a visited location server without doing privacy checks. The requesting server may then believe the home location server did perform the privacy checks and therefore would return the result to a possibly unauthorized LCS Client.
Another problematic situation may occur where the location service node initially receiving the location request from a client believes it shall act as a visited location server when it is expected to play the role of a home location server. If the location server acts as a visited location server, it will go straight to positioning the target user without the privacy or any other checks. It is possible, that the target user may not be in this area, and so an error message may be returned. Although the client does not get the location information, the error message is sent for incorrect reasons. Authorized clients may not receive the information they should have received. This is an unnecessary error situation since the target user could be located by the visited location server. However, since the home location server is incorrectly trying to accomplish the positioning, an error occurs.